Two Las Vegas police officers were killed in a lunchtime ambush Sunday by a man and a woman who later killed a third person before turning weapons on themselves in a Walmart.

Sheriff Doug Gillespie said the officers were eating lunch at a restaurant, CiCi's Pizza, when they were shot by two assailants. One of the officers was able to return fire, Gillespie said.

The suspects then killed a third person at a nearby Walmart, he said.

"It appears the female suspect shot the male suspect, then took her own life,'' Gillespie said.

Killed were Alyn Beck, 41, a Las Vegas officer for more than a dozen years, and Igor Soldo, 31, an officer for eight years. Beck leaves behind a wife and three children, and Soldo is survived by a wife and baby, police said.

"What precipitated this event we do not know,'' the sheriff said. "My officers were simply having lunch.''

The shooting spree that left five people dead began around 11:30 a.m. when a man and woman walked into a pizza restaurant and shot two officers eating lunch, Las Vegas police spokesman Larry Hadfield said.

One of the suspects yelled, "This is a revolution," but the motive for the shooting remains under investigation, Hadfield said.

The two fled to a Walmart across the street, where they shot a person inside, Hadfield said.

"We don't know anything about the suspects yet and are trying to learn more,'' he said.

Pauline Pacheco was shopping at Wal-Mart when she saw the armed man and grabbed her father to escape, KLAS-TV reported.

"We saw when the man was walking, he was shouting, yelling bad words, and suddenly he had a gun," she told the station. "It was terrible, it was terrible. That man was crazy."

Assistant Sheriff Kevin McMahill said the male suspect yelled "everyone get out" before shooting at Wal-Mart. The suspects then walked to the back of the store, he said.

Gov. Brian Sandoval said he was devastated by the deaths of the two officers and an innocent bystander in an "act of senseless violence."

Las Vegas Mayor Carolyn Goodman called the killings a "cruel act" and praised the officers for dedicating "their lives to protecting all of us in our community."

Wal-Mart expressed its condolences in a statement and that the company is working with police on the investigation. Cici's Pizza said in a statement the company was deeply saddened by the shooting and would keep the location closed until further notice.